1. Field of the Invention
The present invention relates to an automated system for mounting a zigzag (sinuous) spring onto a seat frame, and particularly to a device for chucking the zigzag spring in association therewith.
2. Description of Prior Art
As typically found in an automotive seat, a plurality of zigzag springs are provided on a seat frame within the seat in order to resiliently support an occupant sitting thereon, giving him or her a comfortable seating touch.
Recently, in assemblage of this sort of seat, the zigzag springs are automatically mounted securely on the seat frame by use of a particular spring mounting robot. The spring mounting robot has a movable arm controlled for a programmed automatic actions for transferring and mounting a zigzag spring to a seat frame. That movable arm is provided, at its forward free end, with a chucking device for chucking one of plural zigzag springs supplied from a spring supplier and retaining it for mounting to a seat frame placed on a mounting section.
Conventionally, the chucking device includes a pair of movable pawl portions, each being engageable with the respective both ends of a zigzag spring and movable away from each other in a direction to expand the spring. Such chucking action is caused by an air cylinder, for instance, and thereafter, the chucking device with the zigzag spring is transferred by the arm, under a programmed control, towards a seat frame placed on a mounting section, mounting the spring onto the seat frame such as to engage both ends of the spring over a pair of opposed hangers provided on the side frame portions of seat frame, respectively.
But, the thus-arranged conventional spring chucking device has only one predetermined limited movable range of the two pawl portions for chucking the zigzag spring, and is not designed to vary such pawl portion movable range in order to selectively chuck one of plural different springs with different lengths. As a result, it has been a problem that the spring chucking device is confined to only one kind of zigzag spring, and incapable of chucking other kinds of zigzag springs having different lengths.